U.S. patent application number 10/652007 was filed with the patent office on 2005-05-12 for low dielectric constant fluorine and carbon-containing silicon oxide dielectric material characterized by improved resistance to oxidation.
Invention is credited to Aronowitz, Sheldon, Zubkov, Vladimir.
Application Number | 20050098856 10/652007 |
Document ID | / |
Family ID | 25157747 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050098856 |
Kind Code |
A1 |
Aronowitz, Sheldon ; et
al. |
May 12, 2005 |
Low dielectric constant fluorine and carbon-containing silicon
oxide dielectric material characterized by improved resistance to
oxidation
Abstract
The invention provides a process for forming a low k fluorine
and carbon-containing silicon oxide dielectric material by reacting
with an oxidizing agent one or more silanes containing one or more
organofluoro silanes having the formula
SiR.sub.1R.sub.2R.sub.3R.sub.4, where: (a) R.sub.1 is selected from
H, a 3 to 10 carbon alkyl, and an alkoxy; (b) R.sub.2 contains at
least one C atom bonded to at least one F atom, and no aliphatic
C--H bonds; and (c) R.sub.3 and R.sub.4 are selected from H, alkyl,
alkoxy, a moiety containing at least one C atom bonded to at least
one F atom, and ((L)Si(R.sub.5)(R.sub.6)).sub.n(R.sub.7); where n
ranges from 1 to 10; L is O or CFR.sub.8; each n R.sub.5 and
R.sub.6 is selected from H, alkyl, alkoxy, and a moiety containing
at least one C atom bonded to at least one F atom; R.sub.7 is
selected from H, alkyl, alkoxy, and a moiety containing at least
one C atom bonded to at least one F atom; and each R.sub.8 is
selected from H, alkyl, alkoxy, and a moiety containing at least
one C atom bonded to at least one F atom. Also provided is a low
dielectric constant fluorine and carbon-doped silicon oxide
dielectric material for use in an integrated circuit structure
which contains: silicon atoms bonded to oxygen atoms; silicon atoms
bonded to carbon atoms; and carbon atoms bonded to fluorine atoms;
where the dielectric material also has a characteristic selected
from: (a) the presence of at least one C--C bond; (b) the presence
of at least one carbon atom bonded to from 1 to 2 fluorine atoms;
and (c) the presence of at least one silicon atom bonded to from 0
to 2 oxygen atoms.
Inventors: |
Aronowitz, Sheldon; (San
Jose, CA) ; Zubkov, Vladimir; (Mountain View,
CA) |
Correspondence
Address: |
LSI LOGIC CORPORATION
1621 BARBER LANE
MS: D-106
MILPITAS
CA
95035
US
|
Family ID: |
25157747 |
Appl. No.: |
10/652007 |
Filed: |
August 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10652007 |
Aug 29, 2003 |
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09792691 |
Feb 23, 2001 |
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6649219 |
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Current U.S.
Class: |
257/632 ;
257/E21.26; 257/E21.276; 257/E21.277 |
Current CPC
Class: |
C23C 16/401 20130101;
Y02P 20/129 20151101; C01B 33/126 20130101; H01L 21/31629 20130101;
H01L 21/02126 20130101; H01L 21/02211 20130101; H01L 21/3121
20130101; H01L 21/31633 20130101 |
Class at
Publication: |
257/632 |
International
Class: |
H01L 021/31; H01L
023/58 |
Claims
Having thus described the invention, what is claimed is:
1-35. (canceled)
36. A low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material for use in an integrated circuit
structure comprising: silicon atoms bonded to oxygen atoms; silicon
atoms bonded to carbon atoms; and carbon atoms bonded to fluorine
atoms; wherein said dielectric material also has a characteristic
selected from the group consisting of: (a) the presence of at least
one C--C bond; (b) the presence of at least one carbon atom bonded
to from 1 to 2 fluorine atoms; and (c) the presence of at least one
silicon atom bonded to from 0 to 2 oxygen atoms.
37. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 36 wherein said characteristic
is the presence of at least one C--C bond, and at least one of the
carbon atoms participating in said C--C bond is also bonded to at
least one fluorine atom.
38. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 36 wherein all silicon atoms are
bonded to at least 1 oxygen atom.
39. A low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material for use in an integrated circuit
structure comprising the reaction product of an oxidizing agent and
one or more silanes comprising one or more organofluoro silanes
having the formula SiR.sub.1R.sub.2R.sub.3R.sub.4, wherein: (a)
R.sub.1 is selected from the group consisting of H, a 3 to 5 carbon
organo moiety, and an oxyorgano moiety; (b) R.sub.2 is an
organofluoro moiety; and (c) R.sub.3 and R.sub.4 are independently
selected from the group consisting of the same or different leaving
group, the same or different organofluoro moiety, and the same or
different ((L)Si(R.sub.5)(R.sub.6)).sub.n(R.sub.7); wherein n
ranges from 1 to 5; L is O or (C(R.sub.8).sub.2).sub.m; m ranges
from 1 to 4; each of the n R.sub.5's and n R.sub.6's is
independently selected from the group consisting of the same or
different leaving group and the same or different organofluoro
moiety; R.sub.7 is selected from the group consisting of a leaving
group and an organofluoro moiety; and each of the 2n*m or fewer
R.sub.8's is selected from the group consisting of F and the same
or different organofluoro moiety.
40. (canceled).
41. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said oxidizing agent
comprises hydrogen peroxide.
42. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.1
comprises hydrogen.
43. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.2
comprises an organofluoro moiety containing CF.sub.3.
44. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.2 consists
essentially of C and F atoms.
45. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.2 consists
essentially of C and F atoms alone.
46. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.2
comprises consists essentially of C and F atoms and R.sub.3
consists essentially of an alkyl.
47. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.3 contains
CH.sub.3 moieties.
48. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.4
comprises a leaving group.
49. The low dielectric constant fluorine and carbon-doped silicon
oxide dielectric material of claim 39 wherein said R.sub.4
comprises hydrogen.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The subject matter of this application relates to the
subject matter of copending application docket number 00-445,
entitled "A PROCESS FOR FORMING A LOW DIELECTRIC CONSTANT FLUORINE
AND CARBON-CONTAINING SILICON OXIDE DIELECTRIC MATERIAL
CHARACTERIZED BY IMPROVED RESISTANCE TO OXIDATION", assigned to the
assignee of this application, and filed on the same date as this
application.
[0002] The subject matter of this application relates to the
subject matter of copending application docket number 00-446,
entitled "A PROCESS FOR FORMING A LOW DIELECTRIC CONSTANT FLUORINE
AND CARBON-CONTAINING SILICON OXIDE DIELECTRIC MATERIAL
CHARACTERIZED BY IMPROVED RESISTANCE TO OXIDATION", assigned to the
assignee of this application, and filed on the same date as this
application.
[0003] The subject matter of this application relates to the
subject matter of copending U.S. patent application Ser. No.
09/590,310, filed on Jun. 7, 2000, entitled "A LOW TEMPERATURE
PROCESS FOR FORMING A LOW DIELECTRIC CONSTANT FLUORINE AND
CARBON-CONTAINING SILICON OXIDE DIELECTRIC MATERIAL CHARACTERIZED
BY IMPROVED RESISTANCE TO OXIDATION AND GOOD GAP-FILLING
CAPABILITIES", and assigned to the assignee of this
application.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] This invention relates to integrated circuit structures.
More particularly this invention relates to the formation of a low
dielectric constant (k) fluorine and carbon-containing silicon
oxide dielectric material for use in the formation of integrated
circuit structures.
[0006] 2. Description of the Related Art
[0007] The shrinking of integrated circuits has resulted in levels
of electrically conductive interconnects being placed closer
together vertically, as well as reduction of the horizontal spacing
between the electrically conductive interconnects, such as metal
lines, on any particular level of such interconnects. As a result,
capacitance has increased between such conductive portions,
resulting in loss of speed and increased cross-talk. One proposed
approach to solving this problem of high capacitance is to replace
the conventional silicon oxide (SiO.sub.2) dielectric material,
having a dielectric constant (k) of about 4.0, with another
insulation material having a lower dielectric constant to thereby
lower the capacitance.
[0008] Dobson et al., in an article entitled "Advanced SiO.sub.2
Planarization Using Silane and H.sub.2O.sub.2", published in
Semiconductor International, December 1994, at pages 85-88,
describe the low temperature formation of SiO.sub.2 by reaction of
silane (SiH.sub.4) with hydrogen peroxide (H.sub.2O.sub.2) to
produce a silicon oxide which flows like a liquid and thus exhibits
good gap fill characteristics.
[0009] In an article by L. Peters, entitled "Pursuing the Perfect
Low-K Dielectric", published in Semiconductor International, Volume
21, No. 10, September 1998, at pages 64-74, a number of alternate
dielectric materials are disclosed and discussed. Included in these
dielectric materials is a description of a low k dielectric
material having a dielectric constant of about 3.0 formed using a
Flowfill chemical vapor deposition (CVD) process developed by
Trikon Technologies of Newport, Gwent, U.K. The process is said to
react methyl silane (CH.sub.3--SiH.sub.3) with hydrogen peroxide
(H.sub.2O.sub.2) to form monosilicic acid which condenses on a cool
wafer and is converted into an amorphous methyl-doped silicon oxide
which is annealed at 400.degree. C. to remove moisture. The article
goes on to state that beyond methyl silane, studies show a possible
k of 2.75 using dimethyl silane in the Flowfill process.
[0010] An article by S. McClatchie et al. entitled "Low Dielectric
Constant Oxide Films Deposited Using CVD Techniques", published in
the 1998 Proceedings of the Fourth International Dielectrics For
ULSI Multilevel Interconnection Conference (Dumic) held on Feb.
16-17, 1998 at Santa Clara, Calif., at pages 311-318, also
describes the formation of methyl-doped silicon oxide by the low-k
Flowfill process of reacting methyl silane with H.sub.2O.sub.2 to
achieve a dielectric constant of .about.2.9.
[0011] The incorporation of such carbon-doped silicon oxide
dielectric material into interconnect architecture has been very
attractive not only because of the low k properties, but also
because of the compatibility with conventional silicon process
technologies. Generally these materials remain stable upon
annealing at temperatures of up to 500.degree. C. The carbon doped
silicon oxide materials are characterized by the structure of
amorphous silicon oxide with incorporated methyl groups and
hydrogen species, and are also characterized by a reduced density
in comparison with conventional silicon oxide that can be explained
by the formation of microporosity surrounding the incorporated
methyl groups. Furthermore, such hydrocarbon-modified silicon oxide
dielectric materials deposited by CVD techniques are also
characterized by strong adhesion.
[0012] While such carbon-doped silicon oxide dielectric materials
do exhibit the desired low k (i.e., dielectric constants below
about 3.0), resulting in reduced capacitance of the dielectric
material, a major problem of such carbon-doped silicon oxide is a
low resistance to oxidation during subsequent processing steps that
results in a destruction of the incorporated hydrocarbons and a
resulting increase in the overall dielectric constant of the
dielectric material. The sensitivity to oxidation is thought to be
due to the reactivity of the C--H bonds of the methyl group bonded
to silicon. The unintended removal of the methyl group results in a
more hydrophilic surface that may be responsible for a so-called
"via poisoning" which is observed after via etch and photoresist
strip with oxygen-containing plasma, and is related to suppression
of the surface nucleation in subsequent via liner deposition
steps.
[0013] More recently, Sugahara et al., in an article entitled
"Chemical Vapor Deposition of CF.sub.3-Incorporated Silica Films
for Interlayer Dielectric Applications", published in the 1999
Joint International Meeting, Electrochemical Society Meeting
Abstracts, volume 99-2, Abstract 746, 1999, described the reaction
of trimethyl-fluoromethyl-silane (CF.sub.3Si(CH.sub.3).sub.3) with
an ozone oxidizer at an elevated temperature. Sugahara et al.
stated that the low reactivity of Si-alkyl bonds required the
deposition to be carried at elevated temperatures
(.about.350.degree. C.). The dielectric material formed by the
reaction demonstrated resistance to oxidation by oxygen plasma.
However, the precursor compound used by Sugahara yielded only
approximately 15% CF.sub.3 content in the product dielectric layer.
Further, it is known that dielectric films produced by high
temperature ozone processes are characterized by poor gap-fill,
while continuous shrinkage in feature size of integrated circuit
structure demands an increased gap-fill capability.
[0014] It would, therefore, be desirable to provide a process for
forming a low k silicon oxide dielectric material using precursor
compounds that can provide greater control of the amount of
organofluoro moieties incorporated into the dielectric material. It
would also be desirable to provide, in at least one embodiment, a
low k silicon oxide dielectric material which exhibits the gap-fill
properties and film adherence properties of CVD-formed low k carbon
doped silicon oxide dielectric materials such as discussed by the
Dobson et al., Peters, and McClatchie et al. articles discussed
above, while also maintaining a low formation temperature to
conserve the thermal budget of the integrated circuit structure.
This invention provides these characteristics and provides
additional advantages as well.
SUMMARY OF THE INVENTION
[0015] The invention provides a process for forming a low
dielectric constant fluorine and carbon-containing silicon oxide
dielectric material by reacting with an oxidizing agent one or more
silanes comprising one or more organofluoro silanes having the
formula SiR.sub.1R.sub.2R.sub.3R.sub- .4, where: (a) R.sub.1 is
selected from H, a 3 to 5 carbon organo moiety, and an oxyorgano
moiety; (b) R.sub.2 is an organofluoro moiety; and (c) R.sub.3 and
R.sub.4 are independently selected from the same or different
leaving group, the same or different organofluoro moiety, and the
same or different ((L)Si(R.sub.5)(R.sub.6)).sub.n(R.sub.7); where n
ranges from 1 to 5; L is O or (C(R.sub.8).sub.2).sub.m; m ranges
from 1 to 4; each of the n R.sub.5's and n R.sub.6's is
independently selected from the same or different leaving group and
the same or different organofluoro moiety; R.sub.7 is selected from
a leaving group and an organofluoro moiety; and each of the 2n*m or
fewer R.sub.8's is selected from F and the same or different
organofluoro moiety.
[0016] The invention also provides a low dielectric constant
fluorine and carbon-doped silicon oxide dielectric material for use
in an integrated circuit structure comprising: silicon atoms bonded
to oxygen atoms; silicon atoms bonded to carbon atoms; and carbon
atoms bonded to fluorine atoms; where the dielectric material also
has a characteristic selected from: (a) the presence of at least
one C--C bond; (b) the presence of at least one carbon atom bonded
to from 1 to 2 fluorine atoms; and (c) the presence of at least one
silicon atom bonded to from 0 to 2 oxygen atoms.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a flowsheet illustrating a process of the
invention by reacting, at low temperature, hydrogen peroxide with
an organofluoro silane to form a low k film of fluorine and
carbon-containing silicon oxide dielectric material.
[0018] FIG. 2 is a flowsheet illustrating a process of the
invention by reacting ozone with an organofluoro silane to form a
low k film of fluorine and carbon-containing silicon oxide
dielectric material.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The invention provides a process for forming a low
dielectric constant fluorine and carbon-containing silicon oxide
dielectric material by reacting with an oxidizing agent one or more
silanes which include one or more organofluoro silanes having the
formula SiR.sub.1R.sub.2R.sub.3R.- sub.4, where: R.sub.1 is
selected from H, a 3 to 5 carbon organo moiety, and an oxyorgano
moiety; R.sub.2 is an organofluoro moiety; and R.sub.3 and R.sub.4
are independently selected from the same or different leaving
group, the same or different organofluoro moiety, and the same or
different ((L)Si(R.sub.5)(R.sub.6)).sub.n(R.sub.7); where n ranges
from 1 to 5; L is O or (C(R.sub.8).sub.2).sub.m; m ranges from 1 to
4; each of the n R.sub.5's and n R.sub.6's is independently
selected from the same or different leaving group and the same or
different organofluoro moiety; R.sub.7 is selected from a leaving
group and an organofluoro moiety; and each of the 2n*m or fewer
R.sub.8's is selected from F and the same or different organofluoro
moiety.
[0020] The invention also provides a low dielectric constant
fluorine and carbon-doped silicon oxide dielectric material for use
in an integrated circuit structure, the dielectric material
containing silicon atoms bonded to oxygen atoms, silicon atoms
bonded to carbon atoms, and carbon atoms bonded to fluorine atoms,
where the dielectric material is characterized by the presence of
at least one C--C bond. Also provided is a low dielectric constant
fluorine and carbon-doped silicon oxide dielectric material for use
in an integrated circuit structure containing silicon atoms bonded
to oxygen atoms, silicon atoms bonded to carbon atoms, and carbon
atoms bonded to fluorine atoms, where the dielectric material
contains carbon atoms bonded to from 1 to 2 fluorine atoms. Further
provided is a low dielectric constant fluorine and carbon-doped
silicon oxide dielectric material for use in an integrated circuit
structure containing silicon atoms bonded to oxygen atoms, silicon
atoms bonded to carbon atoms, and carbon atoms bonded to fluorine
atoms, where the dielectric material contains at least one silicon
atom bonded to from 0 to 2 oxygen atoms.
[0021] The low k fluorine and carbon-containing silicon oxide
dielectric material formed in the method of the invention will have
a resultant low dielectric constant relative to silicon oxide or
silicon nitride dielectric materials, and will have an increased
resistance to oxidation relative to traditional carbon-containing
silicon oxide dielectric materials, which contain a large number of
oxidant-sensitive aliphatic C--H bonds.
[0022] As used herein, an "organofluoro silane" is a compound that
contains at least one silicon atom bonded to at least one carbon
atom and at least one carbon atom bonded to at least one fluorine
atom. Similarly, an "organofluoro moiety" is a moiety that contains
at least one carbon atom bonded to at least one fluorine atom.
[0023] Use herein of the term "silanes" refers to
silicon-containing compounds containing at least one silicon atom
bonded to at least one hydrogen atom or bonded to at least one
carbon atom. Exemplary silanes include SiH.sub.4,
SiH.sub.3(CH.sub.3), and SiH.sub.3(CF.sub.3).
[0024] By use of the interchangeable terms "low k" or "low
dielectric constant" herein is meant a dielectric constant below
the dielectric constant of silicon oxide or silicon nitride.
Preferably, a low dielectric constant is a dielectric constant
below about 3.5, and more preferably below about 3.
[0025] The term "aliphatic C--H bond" refers to a C--H bond where
the carbon atom bonded to the hydrogen atom is not in an aromatic
ring; thus, "aliphatic C--H bond", as used herein, includes
alicyclic C--H bonds. Similarly, an "aliphatic hydrogen" is a
hydrogen atom bound to a carbon through an aliphatic C--H bond.
[0026] The term "oxidizing agent" refers to an oxygen-containing
compound capable of reacting with an organofluoro silane to form
one or more Si--O bonds. Exemplary oxidizing agents include
hydrogen peroxide, ozone (O.sub.3), oxygen (O.sub.2), oxides of
nitrogen (N.sub.2O, NO, NO.sub.2), and mixtures thereof. Typically
an oxidizing agent used in the method of the invention will
selectively react with C--F bonds less readily than aliphatic C--H
bonds.
[0027] By use of the term "mild oxidizing agent" is meant an
oxidizing agent, such as a peroxide, capable of oxidizing an
organofluoro silane reactant at a low temperature, and which will
not oxidize sufficiently vigorously to cause the Si--C bonds to
break in preference to Si--H bonds, since cleavage of Si--C bonds
can interfere with the film-forming capabilities of the reaction
product. Typically, a mild oxidizing agent will cause cleavage of
Si--H bonds in preference to Si--C bonds. An exemplary mild
oxidation agent is hydrogen peroxide.
[0028] The term "strong oxidizing agent" means an oxidizing agent
capable of forming Si--O bonds more readily than hydrogen peroxide.
Exemplary strong oxidizing agents include ozone (O.sub.3), oxygen
(O.sub.2), oxides of nitrogen (N.sub.2O, NO, NO.sub.2), and
mixtures thereof.
[0029] The term "silicon-bonded moiety" as used herein refers to an
atom or group of atoms, containing at least one atom bonded to a
silicon atom.
[0030] By use of the term "low temperature" herein is meant a
temperature not exceeding about 25.degree. C., preferably not
exceeding about 10.degree. C., and most preferably not exceeding
about 5.degree. C. Typically, this temperature will be measured by
reference to the temperature of the substrate support.
[0031] The term "link" and grammatic variants thereof, as used
herein refers to an atom or moiety that is bonded to two adjacent
atoms. For example, an oxygen atom that links two silicon atoms
will be bonded to two silicon atoms as follows: Si--O--Si.
Similarly, exemplary organofluoro moieties that link two silicon
atoms will be bonded to two silicon atoms as follows:
Si--CF.sub.2--Si, Si--CF.sub.2--CF.sub.2--Si, and the like.
[0032] The term "leaving group" as used herein refers to a
silicon-bonded moiety that undergoes oxidizing agent-mediated
cleavage from a silicon atom more readily than a moiety having the
formula C.sub.xF.sub.2x+1, where x=1 to 5. Preferably, a leaving
group undergoes oxidizing agent-mediated cleavage from a silicon
atom more readily than a CF.sub.3 moiety. Exemplary leaving groups
include H, organo moieties such as alkyl moieties, and oxyorgano
moieties. As used herein, an "oxyorgano moiety" refers to a carbon
and oxygen-containing moiety where an oxygen atom of the moiety is
bonded to a silicon atom. Exemplary oxyorgano moieties include
--OCH.sub.3 and --OCH.sub.2CH.sub.3.
[0033] As used herein, "alkyl" (where no carbon range is specified)
refers to a 1 to 5 carbon saturated hydrocarbon moiety bonded to a
silicon atom through a carbon atom.
[0034] By use of the term "primary hydrogen" herein is meant
hydrogen atoms bonded in multiples of three to a single carbon atom
which is bonded to only one other non-hydrogen atom; in contrast to
secondary hydrogens which are bonded in multiples of two to a
carbon atom which is bonded to two other non-hydrogen atoms, and to
tertiary hydrogens which are bonded in multiples of one to a carbon
atom which is bonded to three non-hydrogen atoms. Examples of
primary, secondary and tertiary hydrogens, respectively, are (in
bold): Si--CH.sub.3, Si--CH.sub.2--CH.sub.3, and
Si--CH--(CH.sub.3).sub.2.
[0035] Organofluoro Silane
[0036] An organofluoro silane used in the method of the invention
will be a compound of the group having the formula
SiR.sub.1R.sub.2R.sub.3R.sub.4- , according to the formula defined
above.
[0037] R.sub.1
[0038] The silicon atom of the above organofluoro silane formula
will be bonded to an R.sub.1 group, which is selected from H, a 3
to 5 carbon organo moiety, and an oxyorgano moiety. Typically, the
R.sub.1 group will participate in the oxidation reaction of the
process of the invention. Accordingly, during the process of the
invention, the R.sub.1 group will typically be replaced by an
oxygen atom linking two silicon atoms in the low k fluorine and
carbon-containing silicon oxide dielectric material produced by the
process of the invention. Where R.sub.1 is H, and, preferably where
at least one of R.sub.3 or R.sub.4 is also H, the process of the
invention can be carried out using a mild oxidizing agent or a
strong oxidizing agent. In one embodiment, a mild oxidizing agent
is used at low temperature in a process with excellent gap-filling
properties.
[0039] Where R.sub.1 is a 3 to 5 carbon organo moiety, R.sub.1 will
often be a saturated alkyl and contain more secondary hydrogen
atoms than primary hydrogen atoms. While not intending to be
limited by the following theory, it is thought that secondary
hydrogen atoms are more susceptible to oxidation relative to
primary hydrogen atoms. This susceptibility to oxidation is
described in detail in U.S. patent application Ser. No. 09/274,457,
which is incorporated herein by reference. Accordingly, when
R.sub.1 contains more secondary hydrogen atoms than primary
hydrogen atoms, R.sub.1 may have an increased propensity for
cleavage when reacted with an oxidizing agent in the process of the
invention. When R.sub.1 is a saturated alkyl, R.sub.1 has more
secondary hydrogens than primary hydrogens when R.sub.1 contains 3
or more carbon atoms (e.g., a --CH.sub.2--CH.sub.2--CH.sub.3 moiety
has four secondary hydrogens and three primary hydrogens).
Similarly, tertiary hydrogens are considered to be more sensitive
to oxidation than are secondary hydrogens. Accordingly, in one
embodiment it may be desirable for R.sub.1 to contain at least one
tertiary hydrogen (e.g., --CH--(CH.sub.3).sub.2).
[0040] The oxidizing agent and reaction conditions of the process
of the invention used when R.sub.1 is an alkyl or a substituted
alkyl will be selected according to the oxidation sensitivity of
R.sub.1 . When R.sub.1 is very sensitive to oxidation (e.g.,
R.sub.1 is hydrogen), the process of the invention can be carried
out using a mild oxidizing agent at low temperature. When R.sub.1
is less sensitive to oxidation (e.g., R.sub.1 is an alkyl), the
selected oxidizing agent can be a strong oxidizing agent, and the
temperature can be increased during the oxidation or a plasma
enhanced oxidation can be carried out. While the sensitivity to
oxidation of R.sub.1 can be an important factor in the selection of
oxidizing agent and reaction conditions, such selections can also
be influenced by other moieties bonded to the silicon atom of the
above formula.
[0041] Where R.sub.1 is an oxyorgano moiety, the oxygen atom will
be bonded to the silicon atom. While not intending to be limited to
the following theory, carrying out the process of the invention by
reacting oxyorgano moieties bonded to silicon with a strong
oxidizing agent at high temperature may result in simpler and more
direct reaction pathways leading to the formation of the low k
fluorine and carbon-containing silicon oxide dielectric material
product relative to the more complex and indirect reaction pathways
associated with use of organo moieties such as alkyl moieties.
[0042] R.sub.2
[0043] The silicon atom of the above organofluoro silane formula
will also be bonded to an organofluoro moiety (R.sub.2) containing
at least one carbon atom bonded to at least one fluorine atom. This
R.sub.2 organofluoro moiety will typically be characterized by the
absence of aliphatic C--H bonds (i.e., the absence of aliphatic
hydrogens), since aliphatic C--H bonds can be more readily oxidized
than C--F bonds. Preferably, the organofluoro moiety will consist
essentially of: (1) one or more carbon atoms; and (2) one or more
fluorine atoms. For example, the organofluoro moiety can be a
saturated fluorocarbon having the general formula
C.sub.xF.sub.2x+1, where x ranges from 1 to 5; for example,
--CF.sub.3, --CF.sub.2CF.sub.3, --CF(CF.sub.3).sub.2,
--CF.sub.2CF.sub.2CF.sub.3, --CF.sub.2CF.sub.2CF.sub.2CF.sub.3,
--CF.sub.2CF(CF.sub.3).sub.2, --C(CF).sub.3, and the like. The
number of carbon atoms in the organofluoro moiety can range from 1
to 5, though the number of carbon atoms preferably ranges from 1 to
4, more preferably ranges from 1 to 3, most preferably ranges from
1 to 2, and typically is 1.
[0044] In another embodiment, the organofluoro moiety of R.sub.2
contains 2 or more carbon atoms. When the organofluoro moiety
contains 2 or more carbon atoms, the moiety will contain at least
one carbon atom that is bonded to both another carbon atom and to a
fluorine atom as follows: C--C--F. Further, a organofluoro moiety
containing 2 or more carbon atoms will typically contain one or
more carbons that are bonded to from 1 to 2 fluorine atoms. For
example, CF(CF.sub.3).sub.2 contains a carbon atom bonded to only
one fluorine atom, and CF.sub.2CF.sub.3 contains a carbon atom
bonded to only two fluorine atoms.
[0045] Alternatively, an organofluoro moiety can contain one or
more aromatic rings, so long as it also contains at least one
carbon atom bonded to a fluorine atom. In one such case, the carbon
atom bonded to the fluorine atom is an aliphatic carbon. For
example, organofluoro moieties having one or more aromatic rings
can include --Ph--CF.sub.3, --CF.sub.2--Ph,
--CF.sub.2--Ph--CF.sub.3, and the like, where Ph is a six carbon
aromatic ring. Since aromatic C--H bonds are more resistant to
oxidation relative to aliphatic C--H bonds, the aromatic C--H bond
will not be readily oxidized by the oxidizing agent used in the
method of the invention. Similarly, an organofluoro silane may
contain an aromatic moiety bound to silicon which aromatic moiety
does not contain fluorine atoms, so long as at least one other
silicon-bonded moiety of the organofluoro silane contains at least
one carbon atom bonded to at least one fluorine atom.
[0046] R.sub.3 and R.sub.4
[0047] The balance of the moieties bonded to the silicon atom of
the above formula are selected from: the same or different leaving
group, the same or different organofluoro moiety, and the same or
different ((L)Si(R.sub.5)(R.sub.6)).sub.n,(R.sub.7), as defined
below. When either R.sub.3, R.sub.4, or both R.sub.3 and R.sub.4
are leaving groups, these moieties can be used to react with the
oxidizing agent in the process of the invention, as discussed above
in regard to R.sub.1. While R.sub.1, R.sub.3 and R.sub.4 can be
identical, such is not required. For example, it may be that
R.sub.1 is desired to be more sensitive to oxidation than R.sub.3
or R.sub.4; in such an instance, R.sub.1 can be, for example, H,
while R.sub.3 and R.sub.4 can be, for example, both alkyls, or an H
and an alkyl. Accordingly, neither R.sub.3 nor R.sub.4 is required
to have more secondary hydrogens than primary hydrogens, and, thus
each can be 1 to 5 carbon organo moiety such as a 1 to 5 carbon
alkyl. In one embodiment, at least one of R.sub.3 and R.sub.4 is
H.
[0048] When either R.sub.3, R.sub.4, or both R.sub.3 and R.sub.4
contain at least one carbon atom bonded to at least one F atom,
such will be a organofluoro moiety or moieties as described above
for R.sub.2.
[0049] R.sub.3, R.sub.4, or both, can also be
((L)Si(R.sub.5)(R.sub.6)).su- b.n(R.sub.7), where: n ranges from 1
to 5; L is O or (C(R.sub.8).sub.2).sub.m; m=1 to 4; each of the n
R.sub.5's and n R.sub.6's is independently selected from the same
or different leaving group and the same or different organofluoro
moiety; R.sub.7 is selected from a leaving group and an
organofluoro moiety; and each of the 2n*m or fewer R.sub.8's is
selected from F and the same or different organofluoro moiety. As
used herein, "*" represents the mathematical multiplication
function. Thus, n*m represents n multipled by m. For example, if n
is 2 and m is 3, n*m is 2 multiplied by 3, which equals 6.
[0050] When either R.sub.3 or R.sub.4 is
((L)Si(R.sub.5)(R.sub.6)).sub.n(R- .sub.7), the organofluoro silane
will contain at least two silicon atoms linked by either an oxygen
atom or one or more carbon atoms. When the two silicon atoms are
linked by one or more carbon atoms, the linking carbon atom(s) are
also bonded to one or more fluorine atoms, or to one or more
organofluoro moieties, or to a combination thereof. The number of
carbon atoms linking two silicon atoms can range from 1 to 4 carbon
atoms, preferably 1 to 3 carbon atoms, more preferably from 1 to 2
carbon atoms, and typically is 1 carbon atom. While such an
organofluoro silane contains two silicon atoms, this compound can
further contain additional silicon atoms. For example, an
organofluoro silane can contain from 2 to 6 silicon atoms,
preferably from 2 to 4 silicon atoms, more preferably from 2 to 3
silicon atoms. Typically such an organofluoro silane will contain 2
silicon atoms. It is within the scope of the invention that an
organofluoro silane containing three or more silicon atoms can
contain one or more oxygen atoms linking silicon atoms while also
containing one or more carbon atoms linking silicon atoms. For
example, an organofluoro silane can contain an oxygen atom linking
a first set of two silicon atoms while also containing a carbon
atom linking a second set of two silicon atoms, shown as:
Si--O--Si--C--Si. Typically however, an organofluoro silane will
contain only oxygen atoms linking silicon atoms or only carbon
atoms linking silicon atoms.
[0051] The use of a multiple-silicon atom-containing compound in
the method of the invention will permit incorporation of a greater
variety of organofluoro moieties, including organofluoro silanes
containing two silicon atoms linked by one or more carbon atoms.
Use of these organofluoro silanes will permit enhanced control of
the number of fluorine and carbon atoms incorporated into the final
low k silicon oxide dielectric material produced using the method
of the invention.
[0052] Compound--Overall
[0053] In one embodiment of the invention, the process of the
invention utilizes organofluoro silanes having few or no aliphatic
hydrogen atoms. For example, a compound such as
SiH.sub.2(CH.sub.3)(CF.sub.3) contains one silicon atom, three
fluorine atoms, and three aliphatic hydrogens; and
SiH.sub.2(Ph)(CF.sub.3) contains no aliphatic hydrogens. Other
exemplary compounds having few aliphatic hydrocarbons include
SiH(CH.sub.3).sub.2CF.sub.3, SiH.sub.2(OCH.sub.3)CF.sub.3,
SiH(OCH.sub.3).sub.2CF.sub.3,
SiH(CH.sub.3).sub.2(CF.sub.3)OSiH(CH.sub.3)- .sub.2(CF.sub.3), and
the like. Typically, such organofluoro silanes having few or no
aliphatic hydrogens contain at least 1 silicon atom per 8 aliphatic
hydrogen atoms. Alternatively, such organofluoro silanes contain at
least 3 fluorine atoms per 8 aliphatic hydrogen atoms.
[0054] In another embodiment, the organofluoro silane has a
relatively large number of fluorine atoms. For example, the
organofluoro silane can contain at least one fluorine atom per
carbon atom. In another example, the organofluoro silane can
contain at least four fluorine atoms per silicon atom. An exemplary
compound that has at least one fluorine atom per carbon atom is
(CH.sub.3).sub.2(CF.sub.3)SiOSi(CH.sub.3).sub.2(CF.sub- .3); and an
exemplary compound that has at least four fluorine atoms per
silicon atom is SiH(CH.sub.3).sub.2(CF.sub.2CF.sub.3).
[0055] In another embodiment, an organofluoro silane will consist
essentially of: one or more silicon atoms; one or more carbon
atoms; one or more fluorine atoms; one or more hydrogen atoms,
where the hydrogen atoms are bonded only to silicon atoms; and,
optionally, one or more oxygen atoms bonded to silicon atoms.
[0056] In one embodiment, it is desirable that some carbon atoms be
incorporated into the backbone of the polymer product (the low k
dielectric material) to enhance the thermal conductivity of the
resultant dielectric film. Thus a silicon oxide containing fluorine
and carbon atoms may have, for example, the structure:
[0057] (I) 1
[0058] where one or more carbon atoms are incorporated into the
silicon/oxygen chain. Such materials can be formed, for example,
using organofluoro silanes having a --CF.sub.2-- linking two
silicon atoms. For example, the organofluoro silane used to form
the material of structure I can be
H.sub.2CF.sub.3SiCF.sub.2SiCF.sub.3H.sub.2.
[0059] Oxidizing Agent
[0060] The oxidizing agent used in the method of the invention can
be any oxygen-containing compound capable of reacting with an
organofluoro silane to form a Si--O bond. For particular reactions,
the oxidizing agent will be capable of reacting with a Si--H bond
in forming the Si--O bond. The oxidizing agent will selectively
react with aliphatic C--H bonds more readily than with C--F bonds.
Exemplary oxidizing agents capable of such reactions include
hydrogen peroxide, oxygen, ozone, and oxides of nitrogen (N.sub.2O,
NO, NO.sub.2). Preferably, the oxidizing agent selectively cleaves
Si--H bonds and aliphatic C--H bonds in preference over Si--O
bonds, or C--F bonds. In one embodiment, the oxidizing agent also
selectively cleaves Si--H bonds in preference over cleaving
aromatic C--H bonds.
[0061] In another embodiment, an oxidizing agent for use in the
method of the invention is a mild oxidizing agent, for example,
hydrogen peroxide. A mild oxidizing agent reactant preferably
comprises a vaporous source of peroxide. Such a peroxide can be
conveniently obtained by flash evaporation of concentrated (30 vol.
% or more) liquid hydrogen peroxide. By the term "source of
peroxide" is meant any material capable of being heated (such as
liquid hydrogen peroxide), or decomposed and heated (such as
calcium peroxide or barium peroxide), toprovide a vaporous hydrogen
peroxide (H.sub.2O.sub.2) oxidizing agent. Hydrogen peroxide will
typically be selected as an oxidizing agent when an organofluoro
silane used in the method of the invention contains Si--H
bonds.
[0062] In contrast, when the organofluoro silane does not contain
Si--H bonds or contains aliphatic C--H bonds, it may be desirable
to use an oxidizing agent which is more reactive than hydrogen
peroxide, for example, oxygen or ozone. In such instances it may
further be desirable to carry out the oxidation reaction using a
plasma enhanced chemical vapor deposition method.
[0063] Reaction Conditions
[0064] The organofluoro silane and the oxidizing agent can be
reacted together by introducing them into a reaction chamber and
carrying out chemical vapor deposition. For example, an
organofluoro silane and hydrogen peroxide are introduced into a
reaction chamber containing a cooled substrate support therein on
which is mounted a semiconductor substrate such as a silicon
substrate on which the reaction product will deposit. For such a
reaction, the reaction chamber is advantageously maintained at a
pressure of from about 0.1 Torr to about 50 Torr, preferably from
about 1 Torr to about 10 Torr, and most preferably from about 1
Torr to about 5 Torr. Both the organofluoro silane and the hydrogen
peroxide are introduced into the chamber in a gaseous or vaporous
phase. The delivery system for the reactants is preferably
maintained at a temperature which ensures delivery of the reactants
into the chamber as gases or vapors, typically from about
70.degree. C. to about 100.degree. C. Flow rates of the individual
reactants will depend upon chamber size and will also vary with the
particular reactants. During the reaction and deposition, the
temperature of the substrate support in the reaction chamber is
maintained at a low temperature not exceeding about 25.degree. C.,
preferably not exceeding about 10.degree. C., and most preferably
not exceeding about 5.degree. C. The reaction and deposition is
carried out for a period of time sufficient to form the layer of
low k fluorine and carbon-containing silicon oxide dielectric
material to the desired thickness over the integrated circuit
structure already formed on the silicon substrate. Usually this
thickness will range from a minimum of about 300 nm to ensure
sufficient electrical insulation between underlying conductive
regions and conductive regions to be formed over the low k
dielectric material up to a maximum of about 800 nm or more.
Thicker layers can be formed, but are deemed unnecessary and merely
add to the bulk of the structure. Such a reaction method forms a
low k film having excellent via-filling properties, yields a
dielectric layer with low adhesion stress, and can be preferable
when using silane compounds that, under particular conditions, can
be oxidized by mild oxidizing agents such as peroxide.
[0065] In another embodiment, the organofluoro silane and oxidizing
agent reactants can be reacted together by introducing gaseous or
vaporous organofluoro silane or an organofluoro silane-containing
mixture and a strong oxidizing agent into a chamber at about 40
Torr to about 1000 Torr, preferably from about 700 Torr to about
800 Torr. The reaction can then be carried out at a temperature
from about 250.degree. C. to about 450.degree. C., preferably from
about 250.degree. C. to about 400.degree. C., and typically about
350.degree. C. The strong oxidizing agent used in the reaction can
be any oxygen-containing reagent capable of reacting with an
organofluoro silane to form a low k fluorine and carbon-containing
silicon oxide dielectric material, such as ozone (O.sub.3), oxygen
(O.sub.2), oxides of nitrogen (N.sub.2O, NO, NO.sub.2), and the
like. The reaction and deposition is carried out for a period of
time sufficient to form the layer of low k fluorine and
carbon-containing silicon oxide dielectric material to the desired
thickness over the integrated circuit structure already formed on
the silicon substrate. Usually this thickness will range from a
minimum of about 300 nm to ensure sufficient electrical insulation
between underlying conductive regions and conductive regions to be
formed over the low k dielectric material up to a maximum of about
800 nm or more.
[0066] In yet another embodiment, a plasma-enhanced chemical vapor
deposition (PECVD) can be carried out. A plasma-activated strong
oxidizing agent and a gaseous or vaporous organofluoro silane or an
organofluoro silane-containing mixture and a carrier gas such as
helium can be introduced into a chamber at about 1 Torr to about 40
Torr, preferably from about 5 Torr to about 20 Torr. The reaction
can then be carried out at a temperature from about 50.degree. C.
to about 450.degree. C., preferably from about 200.degree. C. to
about 300.degree. C., and typically about 250.degree. C. The strong
oxidizing agent used in the reaction can be any oxygen-containing
reagent capable of reacting with an organofluoro silane to form a
low k fluorine and carbon-containing silicon oxide dielectric
material, such as ozone (O.sub.3), oxygen (O.sub.2), oxides of
nitrogen (N.sub.2O, NO, NO.sub.2), and the like. Typically, the
strong oxidizing agent will be oxygen. The reaction and deposition
is carried out for a period of time sufficient to form the layer of
low k fluorine and carbon-containing silicon oxide dielectric
material to the desired thickness over the integrated circuit
structure already formed on the silicon substrate. Usually this
thickness will range from a minimum of about 300 nm to ensure
sufficient electrical insulation between underlying conductive
regions and conductive regions to be formed over the low k
dielectric material up to a maximum of about 800 nm or more.
[0067] The choice of reaction protocol to be used in the method of
the invention can be based on any of a variety of factors, for
example: physical properties of the deposited film such as film
stress; thermal budget of the integrated circuit structure; desired
speed and efficiency of the oxidation reaction; and the like. The
choice of reaction to be used can particularly be influenced by the
nature of the organofluoro silane compound used in the method of
the invention. For example, when an organofluoro silane has as
leaving groups solely hydrogen atoms, the low temperature, mild
oxidizing agent oxidation reaction will typically be preferred to a
strong oxidizing agent oxidation reaction. However, when an
organofluoro silane has as leaving groups solely organo or
oxyorgano moieties, the low temperature, mild oxidizing agent
oxidation reaction will not typically result in complete oxidation
of the organofluoro silane; therefore, use of a strong oxidizing
agent in a high temperature CVD or PE-CVD reaction will be
preferable. For those organofluoro silanes having both hydrogen
atoms and organo or oxyorgano moieties as leaving groups, the
preferred oxidation method will be selected based on the quantity
of a particular type of leaving group that is present in the
organofluoro silane relative to the quantity of silicon atoms
present. For example, when there are present two or more organo or
oxyorgano leaving groups, or a combination thereof, per silicon
atom in an organofluoro silane, an oxidation reaction using a
strong oxidizing agent will be preferred. In other instances,
particularly when there are present two or more hydrogen atoms per
silicon atom, the low temperature, mild oxidizing agent oxidation
reaction will be preferred.
[0068] While not intending to be limited to the following theory,
it is thought that, as the polymer forms, bonds of the organofluoro
moieties to the silicon atoms of the silicon oxide polymer will not
be oxidized as readily as bonds of unsubstituted alkyl moieties to
the silicon atoms of the silicon oxide polymer. Furthermore, the
dielectric constant of the resulting dielectric material having
fluorocarbon groups substituted for alkyl groups should not be
adversely affected by the higher polarizability of the fluorocarbon
groups because of the higher volume of the fluorocarbon group over
the alkyl group, since the dielectric constant is obtained by
dividing the polarizability (a) by the volume (v) in the formula
k=.alpha./v and increases in polarizability tend to be canceled out
by increases in volume.
[0069] Silane Mixtures
[0070] While the product of the process invention principally
comprises a low dielectric constant (low k) silicon oxide
dielectric material containing organofluoro groups, it is within
the scope of the invention to utilize, in the process of the
invention, mixtures of the organofluoro silanes with non-fluoro
silanes, including SiH.sub.4. Such materials can be blended with
one or more of the above-described organofluoro silanes to enhance
other physical properties of the resultant film of low k dielectric
material. Exemplary physical properties include dielectric
constant, adhesion capabilities, via filling capabilities, surface
stress, and the like.
[0071] For example, to enhance the film forming properties of the
low dielectric constant fluorine and carbon-containing silicon
oxide dielectric material of the invention, one or more
organofluoro silanes can be blended with one or more of the
following non-fluoro silanes:
[0072] a) silanes having no silicon atoms bonded to
carbon-containing groups;
[0073] b) organo silanes containing silicon atoms bonded to one or
more carbon-containing groups having aliphatic C--H bonds (such as
methyl silane used in the Trikon Flowfill process);
[0074] c) organo silanes that do not contain aliphatic C--H bonds,
such as organo silanes containing a silicon atom bonded to an
aromatic carbon group; and
[0075] d) mixtures of any two or more of a), b), and c).
[0076] Such a mixture of silanes which includes one or more
organofluoro silanes may be reacted, for example, with hydrogen
peroxide (H.sub.2O.sub.2) in forming a low k fluorine and
carbon-containing silicon oxide dielectric material. For example, a
mixture of silanes corresponding to mixture a) above could contain
a mixture of silane (SiH.sub.4) and an organofluoro silane having
the formula SiR.sub.1R.sub.2R.sub.3R.sub.4 where R.sub.1 is H,
R.sub.2 and R.sub.3 are CF.sub.3, and R.sub.4 is CH.sub.3. A
mixture of silanes corresponding to mixture b) could contain methyl
silane combined with the organofluoro silane
SiR.sub.1R.sub.2R.sub.3R.sub.4 where R.sub.1 is H, R.sub.2 and
R.sub.3 are CF.sub.3, and R.sub.4 is CH.sub.3. To form a mixture
including both a) and b), one could use both silane and methyl
silane in combination with the organofluoro silane having the
formula SiR.sub.1R.sub.2R.sub.3R.sub.4 where R.sub.1 is H, R.sub.2
and R.sub.3 are CF.sub.3, and R.sub.4 is CH.sub.3. Other examples
of substituted silanes which can be used either singly or in
combination to form mixtures of silanes containing organofluoro
silanes include dimethyl silane, ethyl silane, isopropyl
(1-methylethyl) silane, n-butyl silane, isobutyl (2-methyl propyl)
silane, phenyl silane, and methylenebis-silane.
[0077] As stated above, the amount of such silanes which may be
combined with one or more organofluoro silanes in the method of the
invention will typically be combined as minor components. By use of
the term "minor component" is meant that the one or more
non-fluorosilanes used in a mixture of silanes will comprise less
than 50 volume % of the total volume of the compounds in the
mixture, ensuring that the major component of the mixture comprises
one or more organofluoro silanes. However, it is recognized that in
some instances the enhancement of other properties of the resulting
mixture, e.g., the film forming properties, may justify the use of
more that 50 volume % of other silanes, that is, up to about 70
volume % of other silanes and 30 volume % of one or more
organofluoro silanes, even though such usage may raise the
dielectric constant of the resulting dielectric material.
[0078] When using such mixtures the average dielectric constant of
the dielectric material formed using a mixture of silanes can be
determined for the particular proportions of such dielectric
materials using the formula:
k=.SIGMA..sub.ix.sub.ik.sub.i
[0079] where x.sub.i is the volume fraction of dielectric component
i and k.sub.i is the dielectric constant of the pure dielectric
component. Thus, for example, dielectric materials (a) and (b)
might be added to the low dielectric constant fluorine and
carbon-containing silicon oxide dielectric material of the
invention to enhance the film forming properties of the resulting
mixture. If a mixture is formed comprising 10 volume % of
dielectric material (a), 15 volume % of dielectric material (b),
and 75 volume % of the low dielectric constant fluorine and
carbon-containing silicon oxide dielectric material, the average
dielectric constant of the mixture will comprise the sum of the
products of the dielectric constant of each of the materials times
its volume % in the mixture. If the dielectric constant of the low
dielectric constant fluorine and carbon-containing silicon oxide
dielectric material is 2.4, the dielectric constant of dielectric
material (a) is 3.5, and the dielectric constant of dielectric
material (b) is 3.4, the average dielectric constant k.sub.av would
equal (2.4.times.0.75)+(3.5.times.0.10- )+(3.4.times.0.15)=2.7.
[0080] In Combination with Other Layers
[0081] While the low k fluorine and carbon-containing silicon oxide
dielectric material formed in the method of the invention will have
increased oxidation resistance relative to carbon-doped silicon
oxide dielectric material, it may be desirable to form a thin
conventional (standard k) silicon oxide (SiO.sub.2) or silicon
nitride base layer over the substrate to act as a moisture barrier
layer for such low k fluorine and carbon-containing silicon oxide
dielectric material subsequently formed thereon. A similar moisture
barrier layer may also be formed over such a low k fluorine and
carbon-containing silicon oxide dielectric layer for the same
reasons. Such a barrier layer adjacent the layer of low k fluorine
and carbon-containing silicon oxide dielectric material can be
formed to a thickness of about 50 nanometers (nm) to provide
adequate protection (if deemed necessary) for the low k fluorine
and carbon-containing silicon oxide dielectric layer to be formed
thereon. Thicknesses exceeding this minimum may be used, but are
probably unnecessary and may negatively contribute to an undesired
rise in the overall dielectric constant of the resulting composite
layer. Such barrier layers may then serve to protect the low k
dielectric material during subsequent processing steps.
[0082] In another embodiment, deposition of the low k fluorine and
carbon-containing silicon oxide dielectric material does not result
in 100% filling of the via, for example, when the deposition is
carried out using a strong oxidizing agent. In this instance, a
subsequent step with superior gap-filling properties, such as
deposition using hydrogen peroxide, can be used to fill any void
remaining after the deposition with the strong oxidizing agent. The
silane used in the hydrogen peroxide oxidation step can be
SiH.sub.4, or can be an organo silane, an organofluoro silane, or
any other dielectric material useful for filling voids in vias.
[0083] Similarly, the low k fluorine and carbon-containing silicon
oxide dielectric material formed in the method of the invention may
find utility, for example, as one or more of the low k dielectric
layers described in Ser. Nos. 09/425,552; 09/346,493; 09/426,056;
09/426,061; 09/605,380; 09/607,512; 09/704,164; 09/704,200; all
assigned to the assignee of this invention.
[0084] Product--Dielectric Material
[0085] The low dielectric constant fluorine and carbon-containing
silicon oxide dielectric material produced by the method of the
invention will be suitable for use in integrated circuit
structures. This fluorine and carbon-containing silicon oxide
dielectric material will contain silicon atoms bonded to oxygen
atoms, silicon atoms bonded to carbon atoms, and carbon atoms
bonded to fluorine atoms. In one embodiment of the invention, the
fluorine and carbon-containing silicon oxide dielectric material
will be characterized by the absence of aliphatic C--H bonds. A
fluorine and carbon-containing silicon oxide dielectric material
produced by the method of the invention will have a dielectric
constant below the dielectric constant of silicon oxide or silicon
nitride. Preferably, the dielectric constant of the fluorine and
carbon-containing silicon oxide dielectric material will be below
about 3.5, more preferably below about 3.
[0086] Additionally, the fluorine and carbon-containing silicon
oxide dielectric material will demonstrate superior resistance to
degradation in subsequent processing steps such as, for example,
via etch and photoresist removal steps. While not wishing to be
limited by a particular theory, it is considered that organofluoro
compounds, particularly those that do not contain aliphatic C--H
bonds will have an increased resistance to oxidation. This
resistance will decrease the susceptibility of the fluorine and
carbon-containing silicon oxide dielectric material to physical
degradation which can occur in a variety of manners, such as
thermal instability, solvent absorption, and the like. Thus, the
oxidation-resistant fluorine and carbon-containing silicon oxide
dielectric material will typically contain more Si atoms than
aliphatic C--H bonds.
[0087] In one embodiment, the fluorine and carbon-containing
silicon oxide dielectric material will contain as principal
components only silicon atoms, carbon atoms, fluorine atoms, and
oxygen atoms. Such a fluorine and carbon-containing silicon oxide
dielectric material will not contain a significant number of
hydrogen atoms, and, consequently, will not contain a significant
number of bonds susceptible to oxidation during deposition or
subsequent processing steps.
[0088] In another embodiment, the fluorine and carbon-containing
silicon oxide dielectric material will have a ratio of carbon atoms
to silicon atoms of C:Si greater than about 1:3. As described
above, the introduction of carbon atoms into a dielectric material
has been useful for lowering the dielectric constant of silicon
oxide dielectric materials. By introducing a greater ratio of
carbon atoms to silicon atoms, the dielectric constant can be
lowered even further. A particular choice of C:Si ratio will depend
not only upon the desired dielectric constant, but also upon other
desired physical properties of the dielectric material. Thus, a
desired C:Si ratio can be greater than about 2:3, greater than
about 1:1 or greater than about 3:2.
[0089] Because several components can be combined in a silane
mixture used to form the fluorine and carbon-containing silicon
oxide dielectric material, some silicon atoms may not be bonded to
any carbon atoms, while some carbon atoms may be bonded solely to
other carbon atoms and other fluorine atoms. For example, a silane
mixture can contain SiH.sub.4 and
H(CH.sub.3)(CF.sub.2CF.sub.3)SiOSiH(CH.sub.3)(CF.sub.2CF.sub.3); in
this example, the ratio of C:Si will be a function of the ratio of
H(CH.sub.3)(CF.sub.2CF.sub.3)SiOSiH(CH.sub.3)(CF.sub.2CF.sub.3) to
SiH.sub.4 in the silane mixture. The C:Si ratio will usually be
greater than about 1:3, preferably greater than about 2:3, more
preferably greater than about 1:1, and most preferably greater than
about 3:2. Regardless, such a dielectric material will be
characterized by the presence of C--C bonds, and typically, at
least one of the carbons participating in a C--C bond will be bound
to one or more fluorine atoms.
[0090] In yet another embodiment of the invention, the fluorine and
carbon-containing silicon oxide dielectric material will contain at
least one pair of silicon atoms linked by one or more carbon atoms.
Preferably, at least 1% of the silicon atoms will be linked by one
or more carbon atoms, more preferably at least 10% of the silicon
atoms will be linked by one or more carbon atoms. Typically, such a
carbon atom will also be bonded to: (a) one or more fluorine atoms;
(b) one or more organofluoro moieties; (c) or a combination
thereof. As discussed above, in some instances preferred thermal
properties can result when carbon atoms are incorporated into the
backbone of the dielectric material formed in the process of the
invention. Further, it is desirable to have a relatively large
number of fluorine atoms in the dielectric material formed by the
process of the invention. Such a dielectric material will typically
be formed by the above-described process of the invention where the
process includes reacting with an oxidizing agent an organofluoro
silane containing two silicon atoms linked by one or more carbon
atoms.
[0091] Similarly, in another embodiment, a fluorine and
carbon-containing silicon oxide dielectric material of the
invention contains at least 3 fluorine atoms per silicon atom, and
preferably, at least 4 fluorine atoms per silicon atom.
[0092] In yet another embodiment of the invention, the fluorine and
carbon-containing silicon oxide dielectric material will contain at
least one silicon atom bonded to no more than 2 oxygen atoms.
Preferably, at least 1% of the silicon atoms will be bonded to no
more than 2 oxygen atoms, more preferably at least 10% of the
silicon atoms will be bonded to no more than 2 oxygen atoms. These
silicon atoms will be bonded to carbon atoms that link silicon
atoms or to organofluoro moieties such as those described above for
R.sub.2. Preferably, each silicon atom in the fluorine and
carbon-containing silicon oxide dielectric material is bonded to at
least 1 oxygen atom. As with the above embodiment, such a
dielectric material of the invention can contain at least 3
fluorine atoms per silicon atoms, and preferably, at least 4
fluorine atoms per silicon atom.
[0093] In yet another embodiment of the invention, the fluorine and
carbon-containing silicon oxide dielectric material will contain at
least one silicon atom bonded to no more than 2 oxygen atoms.
Preferably, at least 1% of the silicon atoms will be bonded to no
more than 2 oxygen atoms, more preferably at least 10% of the
silicon atoms will be bonded to no more than 2 oxygen atoms. These
silicon atoms will be bonded to carbon atoms that link silicon
atoms or to organofluoro moieties such as those described above for
R.sub.2. Preferably, each silicon atom in the fluorine and
carbon-containing silicon oxide dielectric material is bonded to at
least 1 oxygen atom. As with the above embodiment, such a
dielectric material of the invention can contain at least 3
fluorine atoms per silicon atom, and preferably, at least 4
fluorine atoms per silicon atom.
[0094] In a further embodiment of the invention, the fluorine and
carbon-containing silicon oxide dielectric material will contain at
least one C--C bond. Preferably, at least 1% of the carbon atoms
will be bonded to one or more other carbon atoms, more preferably
at least 10% of the carbon atoms will be bonded to one or more
other carbon atoms. These carbon atoms will typically be included
in the organofluoro moieties bonded to silicon atoms in the
dielectric material. Accordingly, at least one of the two carbons
participating in the C--C bond will further be bonded to one or
more fluorine atoms. The presence of C--C bonds can be desirable
for lowering the dielectric constant of the fluorine and
carbon-containing silicon oxide dielectric material of the
invention by increasing the number of carbon atoms per silicon atom
and thereby reducing the overall dielectric constant of the
dielectric material.
[0095] In a similar embodiment of the invention, the fluorine and
carbon-containing silicon oxide dielectric material will contain at
least one carbon atom bonded to from 1 to 2 fluorine atoms.
Preferably, at least 1% of the carbon atoms will be bonded to from
1 to 2 fluorine atoms, more preferably at least 10% of the carbon
atoms will be bonded to from 1 to 2 fluorine atoms. Such carbon
atoms will typically be included in the organofluoro moieties
bonded to silicon atoms in the dielectric material. As a result,
the presence of carbon atoms bonded to from 1 to 2 fluorine atoms
will typically imply the presence of more than one carbon atom in
the organofluoro moiety. This can be desirable for lowering the
dielectric constant of the fluorine and carbon-containing silicon
oxide dielectric material of the invention by increasing the number
of carbon atoms per silicon atom and thereby reducing the overall
dielectric constant of the dielectric material.
[0096] Thus, the invention provides a low temperature process for
forming a low k fluorine and carbon-containing silicon oxide
dielectric material exhibiting superior resistance to oxidation
than conventional carbon-doped low k silicon oxide dielectric
materials while also providing good gap-filling capabilities and
low stress adhesion not always found in other fluorine and
carbon-containing silicon oxide dielectric materials.
[0097] The following examples serve to further illustrate the
process of the invention.
EXAMPLE 1
[0098] The following example demonstrates the process of the
invention in the formation of a low k fluorine and
carbon-containing silicon oxide dielectric material at low
temperature using the mild oxidizing agent, hydrogen peroxide.
[0099] Methyl-trifluoromethyl-silane SiH.sub.2(CH.sub.3)(CF.sub.3)
and hydrogen peroxide can be introduced into a reaction chamber
containing a cooled substrate support therein on which is mounted a
silicon substrate on which the reaction product will deposit. The
reaction chamber is advantageously maintained at a pressure of
about 1-5 Torr. Both the methyl-trifluoromethyl-silane and the
hydrogen peroxide are introduced into the chamber in a gaseous or
vaporous phase. The delivery system for the reactants is maintained
at about 100.degree. C., which ensures delivery of the reactants
into the chamber as gases or vapors. Flow rates of the individual
reactants will depend upon chamber size and will also vary with the
particular reactants. During the reaction and deposition, the
temperature of the substrate support in the reaction chamber is
maintained at a low temperature not exceeding about 0-10.degree. C.
The reaction and deposition is carried out for a period of time
sufficient to form the layer of low k fluorine and
carbon-containing silicon oxide dielectric material to the desired
thickness over the integrated circuit structure already formed on
the silicon substrate. Usually this thickness will be a minimum of
about 300 nm to ensure sufficient electrical insulation between
underlying conductive regions and conductive regions to be formed
over the low k dielectric material. Such a reaction method forms a
low k film having excellent via-filling properties, yields a
dielectric layer with low adhesion stress.
EXAMPLE 2
[0100] The following example demonstrates the process of the
invention in the formation of a low k fluorine and
carbon-containing silicon oxide dielectric material using the
strong oxidizing agent, ozone.
[0101] Di-methyl-di-trifluoromethyl-disiloxane
(CF.sub.3)(CH.sub.3)HSiOSiH- (CH.sub.3)(CF.sub.3) and ozone can be
introduced into a reaction chamber containing a silicon substrate
on which the reaction product will deposit. The reaction chamber is
advantageously maintained at a pressure of about 760 Torr. Both the
di-methyl-di-trifluoromethyl-disiloxane and the ozone are
introduced into the chamber in a gaseous or vaporous phase. Flow
rates of the individual reactants will depend upon chamber size and
will also vary with the particular reactants. During the reaction
and deposition, the temperature of the substrate support in the
reaction chamber is maintained at a temperature of about
350.degree. C. The reaction and deposition is carried out for a
period of time sufficient to form the layer of low k fluorine and
carbon-containing silicon oxide dielectric material to the desired
thickness over the integrated circuit structure already formed on
the silicon substrate. Usually this thickness will be a minimum of
about 300 nm to ensure sufficient electrical insulation between
underlying conductive regions and conductive regions to be formed
over the low k dielectric material.
[0102] While a specific embodiment of the process of the invention
has been illustrated and described for carrying out the invention,
modifications and changes of the apparatus, parameters, materials,
etc. used in the process will become apparent to those skilled in
the art, and it is intended to cover in the appended claims all
such modifications and changes which come within the scope of the
invention.
* * * * *